Where a separator intended for use in a fuel cell is composed of a material that used in unmodified form will exhibit high contact resistance with the electrodes of the fuel cell, conventional practice has been to subject the electrode-contacting portions of the separator surface to a gold plating process.
However, where a separator is formed from titanium or titanium alloy, direct electrolytic gold plating of the surface is difficult. This is due to the fact that the surfaces of a separator made of titanium or titanium alloy (herein collectively termed “titanium separator”) will have a film of passive titanium oxide formed on them. On the other hand, gold plating of titanium separators will be possible if nickel plating is carried out first by way of a base plating, followed by subsequent gold plating. However, with separators produced in this way, if any defects are present in the plating on the surface, it is possible that nickel will elute from those sites. Since nickel has adverse environmental effects, there exists a need for a technology enabling gold plating to be carried out directly on titanium. Moreover, this issue is not limited to gold plating, but is widely encountered in instances where precious metal plating is carried out on articles of manufacture or components made of titanium or titanium alloy for which low contact resistance with other electrically conductive components is required.
With a view to addressing the above issues at least in part, it is an object of the present invention to provide a technique for precious metal electroplating of titanium surfaces.
The disclosure of Japanese Patent Application 2006-111514 is incorporated herein by reference.